Discuss RCD and Earth Rod? in the UK Electrical Forum area at ElectriciansForums.net

W

woodhai

Looking for help.

I had a look at a friends flat, he said the walls in his flat were live when he put a Pen type voltage indictaor to the wall. This was after there had been a flood in the flat next door and his walls are soaked, literally. Sure enough the Pen stick did light up but I tested with a fluke and got 34 volts. He showed me an old JB in the kitchen that must have been a socket some time or other but was now above the cooker. The capping on the cables was metal type, (shows how old this is). I measued full mains voltage from the metal capping to earth, this being the bolt head on another socket. I meggered the circuit and found it flat to earth. We chased the wall to remove the capping and cables as the socket is not required, guess what we found, first a hole in the middle which had parted the twin and earths but not punctured them then further up bingo, a nail, through the outer insulation and into the live conductor. The RCD must be knackered as this must have been like this for years, this will be replaced when I fit a new CU.
With regard to earthing, the supply company do not supply an earth connection as the supply comes in from overhead. What is the best option, would it be to put in 2 earth rods in the floor in his shop down stairs, I know his gas supply has just been replaced with a plastic pipe but not sure about his water pipe. What sort of reading is acceptable?

Thanks in advance Ian
Read more: http://www.electriciansforums.net/e...earth-electrode-resistance.html#ixzz2JUXyoK6u
 
Don't even think about sinking rods indoors, you'll be just be wasting both your time and money!! Get them outside and at least a 1m to 1.5m distant from any external walls, so that you won't hit the original builders rubble etc...
 
I still use metal capping! It's not that old. E54 wasn't we talking about this the other day regarding over head supplies and earth connections?

We were, lol!! Might be an idea for the OP to go and check the overhead poles to see if the system has been PME'd, most residential area overhead systems are!!
 
We were, lol!! Might be an idea for the OP to go and check the overhead poles to see if the system has been PME'd, most residential area overhead systems are!!

Depends where you are, in the Midlands from my experience I'd say its about 50/50. The supply industry don't want to supply earths in more rural areas, far too many risks involved for them.

My biggest question to him is why has he decided on 2rods before he has begun knocking one in, and in doors can be fine, so long as they have traditional wooden floors, and there is a label by the cu saying where it is
 
Is the op wanting to know what readings he should be getting from the bonding to the water pipes? If so it shouldn't exceed 0.05 ohms
 
Depends where you are, in the Midlands from my experience I'd say its about 50/50. The supply industry don't want to supply earths in more rural areas, far too many risks involved for them.

My biggest question to him is why has he decided on 2rods before he has begun knocking one in, and in doors can be fine, so long as they have traditional wooden floors, and there is a label by the cu saying where it is

I did say residential areas, rather than rural areas!!!

Spoken by a true believer of the now common short thin twigs!! lol!! Any TT roded system needs at least 2 Rods coupled together if only purely for the stability given in the depth, it will also in almost all circumstances reduce Ra values substantially!!

And no it's not fine to make an indoor TT system, not unless you go pretty ''deep'', as the first metre or so is going to be substantially dry year round!!
 
I did say residential areas, rather than rural areas!!!

Spoken by a true believer of the now common short thin twigs!! lol!! Any TT roded system needs at least 2 Rods coupled together if only purely for the stability given in the depth, it will also in almost all circumstances reduce Ra values substantially!!

And no it's not fine to make an indoor TT system, not unless you go pretty ''deep'', as the first metre or so is going to be substantially dry year round!!

well we can agree to disagree on that, ive never found an issue generally when ive used 1 rod, and on those rare occasions that ive had a higher than 100 ohm reading, ive put 2 in, as for under the floor, some situations necessitate it, and ive always got good readings, else i would still be there knocking more rods in
 
Really, so pray tell me how you achieve stability with a single 1.2m rod??

Do you go back and check the Ra values over the course of a year, of course you don't, otherwise you would know that your readings would be all over the place!! You can only achieve stability with depth, and i can tell you now, a metre long rod ain't ever going to give you stability!!

I've never been that foolish to even consider an indoor location for a rod. If i ever did, it would have to be in a property with a basement, ...but there-in lies another big problem!! lol!!
 
Last edited by a moderator:
Looking for help.

I had a look at a friends flat, he said the walls in his flat were live when he put a Pen type voltage indictaor to the wall. This was after there had been a flood in the flat next door and his walls are soaked, literally. Sure enough the Pen stick did light up but I tested with a fluke and got 34 volts. He showed me an old JB in the kitchen that must have been a socket some time or other but was now above the cooker. The capping on the cables was metal type, (shows how old this is). I measued full mains voltage from the metal capping to earth, this being the bolt head on another socket.
I meggered the circuit and found it flat to earth.
We chased the wall to remove the capping and cables as the socket is not required, guess what we found, first a hole in the middle which had parted the twin and earths but not punctured them then further up bingo, a nail, through the outer insulation and into the live conductor. The RCD must be knackered as this must have been like this for years, this will be replaced when I fit a new CU.
With regard to earthing, the supply company do not supply an earth connection as the supply comes in from overhead. What is the best option, would it be to put in 2 earth rods in the floor in his shop down stairs, I know his gas supply has just been replaced with a plastic pipe but not sure about his water pipe. What sort of reading is acceptable?

Thanks in advance Ian
Read more: http://www.electriciansforums.net/e...earth-electrode-resistance.html#ixzz2JUXyoK6u

what does this mean if its a mistake fair enough if not can you explain?
 

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